Due to decreasing availability and increasing expense of petroleum fuels, as well as the increasing public awareness of the environmental pollution due to by-products of combustion of such fuels, there is a continuous effort to improve the efficiency of fuel consumption in internal combustion engines. In particular, the automotive industry, with the assistance of federal requirements, is ever seeking ways to increase gas consumption efficiency and minimize environmental contamination from the by-products of fuel combustion in the automobile engine.
In a conventional automobile fuel system, fuel is supplied from the fuel tank to the carburetor of the engine by means of a fuel pump located in the fuel line. The pump is designed to provide fuel at all times under constant pressure to the carburetor fuel bowl, and the amount of fuel in the bowl is controlled by an inlet needle valve and float system. As fuel is supplied in metered amounts from the bowl to the venturi section of the carburetor for mixture with air before passing into the engine intake manifold, the bowl is refilled with fuel under a constant pressure from the fuel pump. Since periods of acceleration and heavier load on the engine require a faster supply of fuel to the engine, the constant pressure of the fuel pump must be necessarily high enough to satisfy these peak fuel supply requirements. Due to the high fuel pump pressures required for heavy load conditions, I have discovered that the fuel pump delivers more fuel to the carburetor at idle and no-load conditions than is required by the engine. This excess supply of fuel to the carburetor decreases the fuel consumption efficiency of the engine and produces greater non-combusted by-products of fuel combustion in the engine exhaust.
The invention of my said copending application is directed to a fuel economizer system for internal combustion engines having an automatically adjustable fuel flow control valve located in the main fuel supply line between the fuel pump and the inlet to the carburetor to provide a lower fuel pressure and correspondingly less fuel to the carburetor and engine of the automobile during idle and normal load driving conditions while automatically providing higher fuel pressures and more fuel to the carburetor and engine as higher engine output is required, e.g., during periods of automobile acceleration and when increased load is placed on the engine. More particularly, the control valve of my copending application is automatically adjusted from fully open to partially closed position in response to changes in engine load conditions reflected by changes in vacuum pressure in the intake manifold of the engine. The control valve comprises a rotary valve having a valve plug with generally rectangular cross-sectional fuel flow passage therethrough. The valve is rotatably adjusted between fully open and only partially closed positions by a diaphragm motor connected to the valve stem which communicates by vacuum line to an intake manifold fitting on the engine.
Although the automatically adjusted valve construction of my copending application works well to provide improved fuel economy by varying fuel flow based on engine demand, I have found that its use with a broad range of internal combustion engines having different fuel supply requirements can be improved. In particular, I have found that in engine systems requiring precise metering of small amounts of fuel to the carburetor at idle and low load conditions of operation, when vacuum level is highest in the engine intake manifold, manual adjustment of the degree of maximum closure of the valve must be quite precise to prevent occasional tendency for slight fuel pressure build-up on the downstream side of the valve at the carburetor inlet at idle condition. In such situations, slightly more fuel may be supplied to the carburetor at idle condition than is actually required for optimum fuel economy.